1. Field of the Invention
The present invention relates to a single crystal SiC and a method of producing the same, and more particularly to a single crystal SiC which is used as a semiconductor substrate wafer for a light-emitting diode, an X-ray optical element such as a monochromatic sorter, a high-temperature semiconductor electronic element, and a power device, and also to a method of producing the same.
2. Description of the Prior Art
SiC (silicon carbide) is superior in heat resistance and mechanical strength, and also has good resistance to radiation. In addition, it is easy to perform the valence control of electrons and holes by doping an impurity. Moreover, the SiC has a wide band gap (for example, a single crystal 6H-SiC has a band gap of about 3.0 eV, and a single crystal 4H-SiC has a band gap of 3.26 eV) . Therefore, it is possible to realize large capacity, high frequency, high dielectric strength, and high resistance to environments which cannot be realized by existing semiconductor materials such as Si (silicon) and GaAs (gallium arsenide). For these reasons, the single crystal SiC receives attention and is expected as a semiconductor material for a next-generation power device.
As a method of growing (producing) a single crystal SiC of this type, known are a method in which the single crystal SiC is grown by the sublimation and recrystallization method using a seed crystal, and a high temperature epitaxial method in which, in the case of a high temperature, epitaxial growth is conducted on a silicon substrate by using chemical vapor deposition (namely, CVD), thereby growing a single crystal cubic SiC (.beta.-SiC).
In the above-described conventional production methods, however, the sublimation and recrystallization method in which it is difficult to control growth of the single crystal owing to gas phase crystal growth under a high temperature, has problems such as lattice defects and micropipe defects, wherein pin holes having a diameter of several microns and passing through the crystal in the growing direction remain at about 100 to 1,000/cm.sup.2 in a growing crystal. Such pinholes are called micropipe defects and cause a leakage current when a semiconductor device is fabricated, thus making it difficult to obtain the single crystal SiC having excellent quality. Moreover, in the high-temperature epitaxial method, the temperature of the substrate is high and it is also required to produce a high-pure reducing atmosphere. Therefore, the method has a problem in that it is difficult to conduct the method from the view point of installation. Furthermore, the method has another problem in that, because of epitaxial growth, the crystal growth rate is slow in the degree of several um per hour, thus resulting in a problem of extremely poor productivity of the single crystal SiC.
These problems block a practical use of the single crystal SiC which has superior characteristics as compared with other existing semiconductor materials such as Si and GaAs as described above.